Electric balance clock



ELECTRIC BALANCE CLOCK Filed July 10, 1944 INVENTOR. Jean Fink BY Ail).

Patented Jan. 25, 1949 ELECTRIC BALANCE CLOCK Jean Fink, Delavan, Wis.,assignor to The George W. Borg Corporation, Chicago, Ill., a corporationof Delaware Application July 10, 1944, Serial No. 544,190

4 Claims.

The present invention relates in general to clocks of theelectromagnetically-driven balance type, such as are used inautomobiles, for example; and the object of the invention is to producea new and improved clock of this character.

The invention is concerned more in particular with the arrangement forcontrolling the circuit of the electromagnet which drives the balance.This arrangement preferably includes a switch comprising a relativelyfixed contact and a movable contact mounted on a flexible contactspring, together with means for periodically actuating the contactspring to close the circuit of the electromagnet. For actuating thecontact spring a permanent magnet on the balance arbor may be employed,cooperating with an armature on the contact spring.

The arrangement described in the foregoing operates very satisfactorily,and is especially reliable as regards starting of the clock; but isnevertheless subject to a small amount of sporadic trouble due to thecontacts "sticking" or failing to separate promptly when the actuatingforce is removed. The invention is directed specifically to theelimination of trouble from this source.

According to a feature of the invention means are provided foraccurately adjusting the air gap between the permanent magnet and itsarmature, both in the operated and unoperated positions of the armature.This results in a more efllcient magnetic structure which makes itpossible to use a stiffer contact spring and thus greatly reduce thepossibility of the contacts sticking together. Means is also providedfor accurately adjusting the tension of the contact spring.

According to another feature of the invention means is provided forpositively separating the contacts in the event that sticking shouldtake place and for performing this function in timed relation to therelease of the armature by the permanent magnet so that the motion ofthe balance is not interfered with. In one embodiment of the inventionthis means has the form of a device supported on the balance arbor whichengages the armature, in the event of contact sticking, and mechanicallyseparates the contacts. In a modified form of the invention a polarizedarmature is employed and the permanent magnet is provided with polepieces which cooperate with the polarized armature to restore thecontact spring by magnetic repulsion.

The invention will be described in detail hereinafter, reference beinghad to the accompanying drawings, in which Fig. 1 is a rear view of anautomobile clock emi5, and in the balance cock I. The

2 bodying the invention, with the back frame plate removed to expose theelectromagnet and other Parts;

Fig. 2 is a section on the line 2-2, Fig. 1, showing the permanentmagnet and the contact separating attachment which is associatedtherewith:

Fig. 3 is a plan view of the sheet metal stamping from which the contactseparating attachment is formed;

Fig. 4 is a section through the permanent magnet on the line 4, Fig. 2;

Figs. 5 and 6 and fragmentary views which will be used in explaining theoperation of the contact separating attachment; and

Fig. 7 shows a modified form of the contact separating device, operatingon the principle of magnetic repulsion.

The gear train, drive mechanism, and other parts not concerned with theinvention have been omitted from the drawings. For a full disclosure ofthese details reference may be made to Patent No. 2,356,983, grantedAug. 29, 1944, and Patent No. 2,357,645, granted Sept. 5, 1944.

Referring to the drawings, the various parts of the clock are mounted ona frame which comprises the front plate 2, the center plate 3 and theback plate 4. These plates are held together in spaced relation by meansof the posts or pillars 5, 6 and I, of which only posts 5 and 6 areshown in Fig. 2. The back plate 4 is removable without disturbing any ofthe other parts and is not shown in Fig. 1. The frame is of knownconstruction, except for the bridge member I which extends between theposts I and i, as seen in Figs. 1 and 2. This bridge member ispreferably made from rather heavy stock and serves to stiffen the frame,which is thus given ample strength and rigidity independent of the backplate 4. The bridge member 4 also serves to support the adjusting screws8, i0 and ii, the function of which will be explained more fully lateron. Suiilce it to say at this point that since the screws are carried onthe bridge member 4, which is a rigid and substantial part of the frame,they can be given a final and complete adjustment during the assembly ofthe clock and before the back plate 4 is attached.

The clock includes a balance comprising the ring I 2 which is supportedon the four pole armature II. The armature is in turn supported on thearbor i 4, which is provided with suitable bearings in the frame plateI, see down-turned part usual hairspring is provided, and is locatedinside the balance ring i2.

The balance is driven by an electromagnet which comprises the windingl8, core l8, and the pole pieces and 2|. The pole pieces are supportedon the frame plate 3 as shown. The winding I8 is carried on a spool ofinsulating material which is clamped between the ends of the pole piecesby means of nuts threaded onto the opposite ends of the core I9. Theterminal members 22 and 23 are inserted between the pole pieces and thespool heads and are insulated from the former by means of insulatingwashers. The ends of the winding l8 are connected to the terminalmembers 22 and 23, respectively. A condenser 25 and a resistor 26 areconnected in series between the terminal 23 and the frame plate 3. asshown.

The details of the construction of the electromagnet spool and terminalsare shown and described in Patent No. 2,357,645, previously referred to.

The switch for controlling the circuit of the electromagnet comprises afixed contact member 24, formed integrally with the terminal 23, and acontact spring 21, which is assembled on the post 5 between the squarespacer 28 and the washer 29. This arrangement is shown clearly in Fig.2. For operating the contact spring 21 a small permanent magnet 30 isprovided. This magnet 30 is mounted on the balance arbor l4 andcooperates with an armature 3| mounted on the contact spring.

In explanation of the circuit of the electromagnet, it should bementioned that the back plate 4 carries a terminal (not shown) whichengages the tongue 32 of terminal 22 when the back plate is assembled inthe clock movement. This terminal on the back plate is the live terminalof the clock and is connected to the ungrounded pole of the battery whenthe clock is installed in an automobile. The electromagnet circuit isthen completed over a path which includes the ungrounded pole of thebattery, back plate terminal, terminal 22, winding l8, terminal 23,fixed contact member 24, contact spring 21, the clock frame, and theframe of the automobile, the latter being connected to the grounded pole.of the battery. It will be noted that the condenser 25 and resistor 26are connected in shunt of the switch 2421.

When the electromagnet circuit is open, at the back plate terminal, forexample, the oscillating parts are in the position in which they areshown in Figs. 1 and 2. This is due in part to the hairspring which isso adjusted that the balance is brought to rest in such a position thatthe permanent magnet 30 is opposite armature 3|, or at least withinoperative range of the armature. The permanent magnet, therefore,orients the balance to the position in which it is shown and alsoattracts the armature 3|, thus operating the contact spring 21 andclosing the switch. The

clock is thus maintained in readiness to start when the circuit isclosed.

When the clock is connected up, current starts to flow over the circuitdescribed above and the electromagnet is energized. An impulse is thusgiven to the balance, which rotates it is one direction or the other,causing the permanent magnet 30 to rotate also and release the armature3|, thus opening the circuit of the electromagnet. The rotation of thebalance tensions the hair spring, which shortly stops the. rotation andcauses it to be resumed in the opposite direction, whereupon thepermanent magnet, 'as it'passe's the armature 3|, operates the switchmomen- The adjusting screws 9, l0 and II are threaded into tapped holesin the bridge member 8. Before the holes are tapped, slots such as 33,Fig. 1, are sawed in the bridge member to intersect the holes. Due tothese slots the material is able to yield slightly when the holes aretapped, with the result that the tapped holes are slightly smaller thanthe screws. When the screws are inserted the material again yields, butgrips the screws tightly so that they remain in any adjusted position.This construction enables lock nuts to be dispensed with.

The electromagnet assembly including the terminal 23 and the fixedcontact 24 are so designed and constructed that when the parts areassembled in the clock the fixed contact member 24 is too high, that is,the armature 3| is too far away from the magnet 30 when the armature isin operated position. The screw H is provided so that the air gapbetween the armature 3| and magnet 30 can be accurately adjusted, and isturned down until the air gap is reduced to the desired length. Thecontact member 24 is quite stiii but is adapted to yield sufliciently toenable the adjustment to be made. A small block 34 of insulatingmaterial is inserted between screw II and the contact member 24 to avoida short circuit between the contact member and the frame.

The screw I0 is a back stop for the spring 21 and serves to adjust thestroke of the armature 3|. By adjusting the strokeas short as possibleconsistent with a satisfactory separation of the contacts the air gapbetween the permanent magnet and the armature in retracted positionisreduced to a minimum and the contact spring 21 accordingly may have themaximum tension.

It has been found that a more close and accurate adjustment of the airgap can be made if the contact spring 21 is made substantiallyuni-lexible between the contact and the armature 3| and for somedistance beyond the latter. This is accomplished by providing thecontact spring with an upturned flange along each edge, as shown in thedrawings.

The screw 9 is provided in order to enable the tension in spring 21 tobe adjusted. The spring is tensioned upward and the end of the springrests against the stop screw l0 when the armature 3| is not influencedby the magnet 30. More tension than can be used is put in the springbefore it is assembled and then after assembly the tension is relievedto the desired extent by turning in the screw 8.

The adjusting arrangements described enable the permanent magnet 30 tooperate at maximum 'efllciency and make it possible to have a fairadjusted contact springs, a certain amount of trouble is encountered dueto contact sticking. The exact cause of the trouble does not appearauaoao to be fully understood. The contacts do not weld together, butmerely stick together for some reason or other. They can generally beseparated by a slight jar and may not stick again for a long time, ifever. In the occasional automobile clock in which the trouble isencountered, it manifests itseli by stoppage of the clock for a periodof a few minutes up to an hour or more. This occurs generally at night,when the car is in the garage, as any motion of the car is usuallysuflicient to jar the contacts apart and start the clock running again.

In many devices it is possible to prevent contact sticking, or at leastsubstantially eliminate it, by increasin the spring tension. Thisexpedient has been followed in the case of the clock described herein,as previously explained. The clock is rather small, however, and thereis a limit to the size of the permanent magnet that can be used, whichlimits the amount of spring tension that can be employed. Since it isdesirable in the case of an automobile clock to absolutely eliminate alldanger or even possibility of stoppage, a further improvement isintroduced whereby if contact stickin should occur the contacts arepositively separated, causing the clock to con tinue running as thoughno trouble had occurred.

This improvement will now be described.

Referring to Fig. 2, it will be seen that the permanent magnet has anattachment which includes two arms 40 and 4! located on opposite sidesof the magnet. These arms are in the plane in which the magnetoscillates and accordingly are operatively related to the armature 3|,as will be explained.

The construction of the attachment is illustrated in Figs. 3 and 4.Before forming, it has the shape shown in Fig. 3, being a stamping fromsome non-magnetic sheet metal, preferably beryllium copper, which can behardened after forming. By means of a suitable die the central portionof the blank shown in Fig. 3 is given a semi-circular formation to fitthe lower end of the magnet 30 and at the same time the perforated ear42 is bent at right angles along the dotted line so that it will restagainst the side of the magnet when assembled thereto. Another ear 43may be provided, if desired, to engage the opposite side of the magnet.The formed blank is secured to the magnet by means of a headed metalsleeve 44 which passes through the hole in car 42 and a cor respondinghole in the magnet, in which it has a press fit. The sleeve 44 may beadditionally secured by staking at the end opposite the head. Thecomplete magnet assembly, including the described attachment and thesleeve 44, is carried on the arbor |4.

Reference may now be made to Figs. 5 and 6 for a. more detailedexplanation of the operation of the device. In these figuressemi-circular arcs have been drawn to show the path of the end of themagnet 30 and the path of the ends of the arms 40 and 4|.

In Fig. 5 it is assumed that the magnet assembly is rotating in thedirection of the arrow. The

magnet 30 has just released the armature 3| and the contacts haveseparated in the normal manner due to the tension in spring 21. As theresult of this normal operation the armature 3| has moved outside thepath of the ends of arms 40 and 4| and will not be engaged by arm 40when it passes the armature.

In Fig. 6 the magnet assembly is assumed to be rotating in the oppositedirection, although the direction of rotation is immaterial. The magnet32 has released the armature I l, as in the preceding case, but due tothe contacts sticking together the switch has remained closed and thearmature 3| has remained in attracted position. In this position thearmature is in the path of the end or arm 4|, which engages the armatureand positively separates the contacts.

The arms 40 and 4| should be spaced from the magnet in the plane of itsrotation Just enough so that during normal operation the armature 3|will have time to restore and move out of the path of the arms 40 and 4|before the approaching arm can engage it. As long as the switch operatesnormally. therefore, the arms 40 and 4| perform no function, that is,neither one of these arms will ever engage the armature. In case therestoration of the armature is delayed by contact sticking, however, thearmature is instantly engaged by arm 40 or arm 4|, dependin on thedirection of rotation at the time, the contacts are forcibly separated,and the armature is restored by spring 21 in the usual manner, exceptfor the momentary delay. The only effect produced by the sticking oi thecontacts is a slightly longer impulse to the electromagnet. which doesno harm.

In connection with the foregoing it may be pointed out that when thepermanent magnet is directly aligned with the armature, as shown in Fig.2, the poles of the four pole armature l3 are symmetrically disposedrelative to the poles 20 and 2| and since the armature poles are degreesapart the balance can rotate 45 degrees before a pair of armature polesbecomes aligned with the poles 2D and ii. The switch must open beforethe armature poles reach this aligned position or the continuedenergization of the electromagnet will exert a retarding effect on thebalance. It fo lows, therefore, that the spacing between the permanentmagnet and the arms 40 and 4|, in the particular clock shown, should besomewhat less than 45 degrees. The spacing may be as small as 35degrees. for example, which allows 25 degrees for release of thearmature by the permanent magnet and 10 degrees for normal restorationof the armature by the contact spring.

It will be understood that the principles involved apply to other typesof balance armatures and other types of electromagnet structures andthat in any case the contact separating means will be suitably locatedso that the contacts will be separated in the proper timed relation tothe motion of the balance and its normal oscillations will not beinterfered with.

Attention may now be directed to the modification which is shown in Fig.7. In this embodiment of the invention the permanent magnet 30' has anattachment including the arms 50 and 5| which is similar to theattachment already described except that it is made of magneticmaterial, such as soft iron, for example. The arms 50 and 5| also aresomewhat shorter that the arms 40 and 4|, and the ends or polesoscillate in the same path as the end of thepermanent magnet. Thearmature 3| is polarized, that is, it is a small permanent magnet. Themagnets 3| and 30' are so poled that in the position in which the partsare shown in Fig. 7 the magnet or armature 3| will be attracted to closethe switch.

Describing the operation of this modification briefly, it may be assumedthat the permanent magnet 30' is rotating in a clockwise direction, asshown by the arrow. As the permanent magnet passes the armature 3| thelatter is attracted to close the switch. After further rotation of about25 degrees the armature is released by the permanent magnet and theswitch is opened, assuming normal operation. As the rotation continuesthe arm or pole comes within operative range of the armature 3i with theresult that if the contacts have stuck together the armature 3| isrestored by magnetic repulsion and the contacts are separated. Theoperation during rotation in the other direction is the same except thatarm or pole Si is operative.

In this modification since the poles 50 and 5| become operative withrespect to the armature before coming into alignment therewith theseauxiliary poles should be spaced somewhat farther from the permanentmagnet than the arms 40 and 4! in the other modification.

The application of the magnetic repulsion principle is somewhat morecostly, inasmuch as it requires two permanent magnets instead of one. Ithas the advantage, however, of avoiding all mechanical contact withoscillating parts and the further advantage that the auxiliary polesreduce the length of the air gap and render the permanent magnetsomewhat more efllcient, which makes it possible to use a somewhatstiffer contact spring.

The invention having been described, that,

which is believed to be new and for which the protection of LettersPatent is desired will be pointed out in the appended claims.

I claim:

1. In a clock, an electromagnet, a switch for controlling the circuit ofsaid electromagnet, an oscillatory system driven by said electromagnet,a-polarized armature associated with said switch, and a magneticstructure included in said oscillatory system and adapted to cooperatewith said armature to actuate said switch by magnetic attraction and torestore said switch by magnetic repulsion.

2. In a clock, an electromagnet, a switch for controlling the circuit ofsaid electromagnet, said switch comprising a relatively fixed contactand a movable contact, a contact spring rigidly supported at one end andcarrying said movable contact at the other end, an armature carried bysaid contact spring, an oscillating system driven by said electromagnetand including a permanent magnet cooperating with said armature toperiodically close said switch, and means for stifiening said contactspring to prevent flexing thereof between said armature and movablecontact when the movement of the armature is arrested by closure of theswitch.

3. In a clock, an electromagnet, a switch for controlling the circuit ofsaid electromagnet, an armature for operating said switch, anoscillating system including a permanent magnet for periodicallyattracting said armature, a clock frame on which said part aresupported, and means including adjusting screws threaded in a part ofsaid frame for adjusting the air gap between said permanent magnet andsaid armature in its attracted and non-attracted positions.

4. In a clock, a balance, an electromagnet for driving said balance, aswitch for controlling the circuit of said electromagnet, a frame forsupporting said parts, said frame comprising a front plate, a centerplate, and a removable back plate, means including pillars forsupporting said plates in spaced relation, said center plate being cutaway to provide space for said balance, an auxiliary frame memberextending between two of said pillars to strengthen the frame where saidcenter plate is cut away, and means including screws threaded in saidframe member for adjusting said switch.

JEAN FINK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Fink Mar. 13, 1945

